An inflatable vehicle occupant protection device, such as an air bag, is part of an apparatus which further includes a crash sensor and an inflator. The crash sensor senses vehicle conditions that indicate the occurrence of a crash. When the crash sensor senses a crash-indicating condition of at least a predetermined threshold level, the inflator is actuated. The inflator then emits inflation fluid which inflates the air bag into the vehicle occupant compartment to help protect an occupant of the vehicle.
An air bag and an inflator are typically assembled together as parts of an air bag module which is separate from the crash sensor. The air bag module is located in the vehicle adjacent to the vehicle occupant compartment. For example, a driver's side air bag module may be located on the vehicle steering column. A passenger side air bag module may be located in the vehicle instrument panel.
In addition to the air bag and the inflator, an air bag module typically includes a reaction structure, a retainer structure, and a cover. The reaction structure supports the inflator. The retainer structure encircles the inflator. A mouth portion of the air bag also encircles the inflator, and is clamped between the retainer structure and the reaction structure. The cover includes at least one deployment door which extends directly over the air bag to conceal the air bag and the other parts of the module from the vehicle occupant compartment.
When the inflation fluid emitted from the inflator begins to inflate the air bag, it moves the air bag outward against the deployment door on the cover. The cover is ruptured by the force of the fluid pressure acting on the air bag. The deployment door is then moved pivotally out of the path of the air bag as the air bag is inflated outward from the cover and into the vehicle occupant compartment.